User`s manual

A-4 Appendix A
Hot Rod 100 Pro
Block A
Block B
Block C
Block D
Disk 0 Disk1 Disk 2 Disk3
D 0
C 0
B 0
A 0
D 1
C 1
B 1
A 1
D 2
C 2
B 2
A 2
Hamming
Code
….
Disk 0 Disk1 Disk 2 Disk3
D 0
C 0
B 0
A 0
D 1
C 1
B 1
A 1
D 2
C 2
B 2
A 2
D Parit
y
C Parit
y
B Parit
y
A Parit
y
Block A
Block B
Block C
Block D
Stripe 0, 1, 2
Parity
Stripe 2Stripe 1Stripe 0
ABCD
DATA
Disk 0 Disk1 Disk 2 Disk3
D 0
C 0
B 0
A 0
D 1
C 1
B 1
A 1
D 2
C 2
B 2
A 2
D Parit
y
C Parit
y
B Parit
y
A Parit
y
Block 0, 1, 2
Parity
Block 2Block 1Block 0
RAID Level 2
Disk Striping with error-
correction code (ECC)
RAID 2, which uses Hamming error
correction codes, is intended for use with
drives which do not have built-in error
detection. Because the check method of
Hamming code is very complicated, and
more than one drive is required to store ECC
information, RAID 2 offers no significant
advantages over RAID 3.
RAID Level 3
Parallel transfer with parity
RAID 3 uses a separate drive to store parity
and stripes data on a byte-by-byte basis
across all of the data disks in the array.
Because each I/O accesses all drives in the
array, RAID 3 does not support multiple,
simultaneous read/write requests. It is
optimized for large, sequential data requests.
RAID Level 4
Independent Data disks with
shared parity disk
RAID 4 is identical to RAID 3 except the
block level stripes are used.
RAID 4 supports multiple simultaneous
read requests. However, since all write
operations require that parity data to be
updated each time, they can not be
overlapped. And so the RAID 4 offers no
significant advantages over RAID5.